A method for checking the functional reliability of an image sensor evaluates statistical fluctuations in the grey-scale values provided by the pixels of the image sensor. An actual noise factor, which is derived for light impinging on the pixels, is evaluated. A pixel failure is assumed if the actual noise factor misses a predetermined criterion defined by a reference noise factor. According to one embodiment, the reference noise factor is a dark noise factor. An electronic camera that operates in accordance with the above-described method is also disclosed.